Large Berry phases in layered graphene

TL;DR

This paper investigates large Berry phases in layered graphene systems caused by electrons encircling Dirac points under time-dependent electric fields, proposing an experimental method to measure these phases via electronic Zitterbewegung.

Contribution

It introduces a study of large Berry phases in layered graphene and proposes an experimental approach to measure excess Berry phases through electronic Zitterbewegung.

Findings

Large Berry phases can be acquired in graphene when electrons encircle Dirac points.

A method involving Zitterbewegung near orthogonality points can experimentally determine these phases.

The study highlights the significance of non-concentric electron trajectories around Dirac points.

Abstract

Brillouin zones of graphene systems possess Dirac points, where band degeneracies occur. We study the variety of (and large magnitude) phases that the electronic states can acquire when a uniform time-dependent electric field carries the electrons around one or more Dirac points in a non-concentric fashion. An experimentally accessible determination of excess Berry phases is proposed involving the Zitterbewegung of electronic current near an orthogonality point in adiabatic motion.